Synthesis of multifunctional high strength, highly swellable, stretchable and self-healable pH-responsive ionic double network hydrogels

The multifunctional double network (DN) soft hydrogels reported here are highly swellable and stretchable pH-responsive smart hydrogel materials with sufficient strength and self-healing properties. Such multifunctional hydrogels are achieved using double crosslinking structures with multiple physical and chemical crosslinks. They consist of a copolymer network of acrylamide (AM) and sodium acrylate (Na-AA) and other reversible network of poly(vinyl alcohol)-borax complex. They were characterized by Fourier transform IR analysis and studied for their hydrogen bonding and ionic interaction. The degree of equilibrium swelling was observed to be as high as 5959% (at pH 7.0) for a hydrogel with AM/Na-AA = 25/75 wt% in the network (GS-6 sample). The highest degree of swelling was observed to be 6494% at pH 8.5. The maximum tensile strength was measured to be 1670, 580 and 130 kPa for a DN hydrogel (GS-2 sample: AM/Na-AA =75/25 wt% with 20, 40 and 60 wt% water content, respectively). The self-healing efficiency was estimated to be 69% for such a hydrogel. These multifunctional DN hydrogels with amalgamation of many functional properties are unique in hydrogel materials and such materials may find applications in sensors, actuators, smart windows and biomedical applications. (c) 2018 Society of Chemical Industry